For a rigid cervical collar to be effective, it should rest on which joint and provide support under both sides of which facial structure?

The correct answer highlights the importance of anatomical placement for the effectiveness of a rigid cervical collar. A rigid cervical collar should sit on the sternoclavicular joint, which is the joint where the clavicle meets the sternum, providing essential support and stabilization for the cervical spine.

Additionally, the collar must provide support under both sides of the maxilla, which is the upper jawbone. This positioning is crucial as it helps maintain alignment of the cervical spine and ensures that any potential injury to the neck is properly immobilized. Proper fit of the collar accommodates the contour of the chin and the upper neck, thereby enhancing patient safety and comfort.

Other options mention anatomical locations that are either not relevant to neck stabilization or do not support the cervical spine effectively. For instance, the acromioclavicular joint is located at the shoulder, the temporomandibular joint is associated with jaw movement, and the patellar joint pertains to the knee—all of which are not suitable references for the placement and function of a cervical collar.